Clipped Speech Signals Quality Estimation

Abstract

Clipping of speech leads to the appearance of higher orders harmonics and, as a result, to reducing of accuracy of automatic speech recognition systems used as kind of artificial intellect of aircraft control systems and flight control systems for unmanned aerial vehicles. In this paper, the subjective and objective estimates of clipped speech quality are presented. It was shown that subjective speech quality Degradation Mean Opinion Score scale values are about 4.5, 3.5 and 2.5 for degrees of clipping 5 dB, 10 dB and 15 dB, respectively. Establishing of this rule allows find the boundary permissible degree of clipping based on certain requirements to the speech quality. Dependencies of objective speech quality measures such as segmental signal-to-noise ratio, frequency weighted segmental signal-to-noise ratio, log-spectral distortion, bark-spectral distortion and perceptual evaluation of speech quality on the clipping degree are obtained. Calculations of correlation coefficients and matching maps which establish relationship between objective and subjective speech quality measures have been made. Obtained results allow concluding that objective speech quality measures can be applied to evaluate both the clipped speech quality and the degree of speech signals clipping.